The goal of this research is to develop a more powerful exposure assessment tool that directly measures the deposition of inhaled particles within the human lung. Inhaled particles do not always deposit in the lung. Therefore, a device that estimates the size-specific deposition of inhaled particles in the human lung will improve the power of risk assessment by providing a more physiologically-relevant measure of dose, and hence, inhalation hazard in the workplace. This research will build on a wide-body of existing literature on aerosol inhalation and lung deposition. By integrating this technology into an existing inhalable sampling cassette, (i.e., the IOM sampling cassette) we will be able to reproduce both aerosol inhalability and deposition, allowing for more realistic and reliable hazard assessment. Such integration will aid industry acceptance of our device, being both inexpensive and requiring no purchase of additional sampling technologies. Additionally, the use of a previously validated housing precludes the need for costly aspiration efficiency tests typically associated with aerosol sampler development. The significance of the proposed research is the establishment a more physiologically relevant metric of inhaled aerosol dose. A measurement more closely related to dose will increase our ability to associate the onset of occupational respiratory diseases with specific exposures, which, in turn, will allow for more efficient intervention and control strategies targeted to reduce specific toxic components of workplace atmospheres. Enhancing the predictive power of occupational epidemiology and risk assessment will help regulating agencies better prioritize the long list of existing and emerging aerosol hazards and allow them to establish targeted, health-based exposure standards. Results from this research can also be translated to the larger realm of health-related air pollution outside of the workplace (e.g., indoor air, ambient air pollution), both nationally and internationally in developing countries. [unreadable] [unreadable] [unreadable]